This invention relates to rotating rectifier assemblies for electric machines. More specifically, this invention relates to a rotating rectifier assembly for ac generators having a substrate disposed about a rotating shaft which provides improved heat dissipation.
Self-excited brushless ac generators typically utilize a rotating rectifier assembly to rectify the output of an exciter rotor and to feed the resulting dc voltage to a main generator rotor. Rectifier diodes enclosed in DO-5 cases have been traditionally used in such rotating rectifier assemblies. Such assemblies were acceptable for use in generators which rotated at relatively low speeds and which have space available for the required mounting and the electrical interconnections. Recently, however, the trend in state of the art generators, particularly aircraft generators, has been towards increased generator output ratings and towards reduced generator weight and volume. These recent requirements have increased the current densities which must be generated in the windings of the generator, thereby making power dissipation more difficult.
Earlier rotating rectifier assemblies did not generate the higher current density required in today's aircraft generator and, therefore, did not have the associated heat dissipation problems. Also, earlier rotating rectifier assemblies were large and were typically mounted in a metal casing, thereby alleviating heat dissipation difficulties. The reduced weight and volume coupled with the increased power outputs and speed of today's generators, however, does not permit the use of such earlier rotating rectifier assemblies.
A rotating rectifier assembly which generates higher current outputs and which can provide greater heat dissipation, therefore, is needed.